path: root/doc/syntax/calling_methods.rdoc
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authoraycabta <aycabta@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2018-10-20 10:57:33 +0000
committeraycabta <aycabta@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2018-10-20 10:57:33 +0000
commitecc627b20aa011616d29a765448957c445be7a62 (patch)
tree2878794e0c7497840d09bc79a564f44e1c6dd9fb /doc/syntax/calling_methods.rdoc
parent4d4b60aceac9daceeea1e0fc0112821dbcd10567 (diff)
Improve safe navigation operator's docs [Misc #15109]
* doc/syntax/calling_methods.rdoc: Add Safe navigation operator section. git-svn-id: svn+ssh:// b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'doc/syntax/calling_methods.rdoc')
1 files changed, 23 insertions, 4 deletions
diff --git a/doc/syntax/calling_methods.rdoc b/doc/syntax/calling_methods.rdoc
index ec86ef05ee..b86d60ad88 100644
--- a/doc/syntax/calling_methods.rdoc
+++ b/doc/syntax/calling_methods.rdoc
@@ -27,13 +27,32 @@ This sends the +my_method+ message to +my_object+. Any object can be a
receiver but depending on the method's visibility sending a message may raise a
-You may use <code>&.</code> to designate a receiver, then +my_method+ is not
-invoked and the result is +nil+ when the receiver is +nil+. In that case, the
-arguments of +my_method+ are not evaluated.
You may also use <code>::</code> to designate a receiver, but this is rarely
used due to the potential for confusion with <code>::</code> for namespaces.
+=== Safe navigation operator
+<code>&.</code>, called "safe navigation operator", allows to skip method call
+when receiver is +nil+. It returns +nil+ and doesn't evaluate method's arguments
+if the call is skipped.
+ REGEX = /(ruby) is (\w+)/i
+ "Ruby is awesome!".match(REGEX).values_at(1, 2)
+ # => ["Ruby", "awesome"]
+ "Python is fascinating!".match(REGEX).values_at(1, 2)
+ # NoMethodError: undefined method `values_at' for nil:NilClass
+ "Python is fascinating!".match(REGEX)&.values_at(1, 2)
+ # => nil
+This allows to easily chain methods which could return empty value. Note that
+<code>&.</code> skips only one next call, so for a longer chain it is necessary
+to add operator on each level:
+ "Python is fascinating!".match(REGEX)&.values_at(1, 2).join(' - ')
+ # NoMethodError: undefined method `join' for nil:NilClass
+ "Python is fascinating!".match(REGEX)&.values_at(1, 2)&.join(' - ')
+ # => nil
== Arguments
There are three types of arguments when sending a message, the positional